Title (fr)

Publication

Application

Priority

DE 19844176 A 19980925

Abstract (en)

To separate and remove low molecular portions of molten polyamide 6 and copolyamide, they are extracted by vacuum suction where the vacuum development and the condensation of the low molecular compounds are combined in a fluid jet pump (II) operated by caprolactam. The material exchange apparatus (I) is a precipitation film evaporator, thin film evaporator or degassing extruder, heated to 225-300 degrees C. The degassing extruder is a multi-screw extruder type. The vacuum suction line is heated from the melting temp. of the material exchange apparatus up to 300 degrees C, and is linked to the fluid jet pump. The pump is fed with liquid caprolactam (d) at a temperature of 75-100 degrees C, to generate a vacuum of 1.0 kPa absolute. The liquid caprolactam is recirculated with dissolved oligomers, in a circuit which has a skimming vessel (III) with an overflow and a recirculating pump (IV) which forces the caprolactam back to the jet pump to drive it. The processed molten material is passed directly to further processing stages, or is immediately granulated for further use. The immediate further processing delivers additives, for thermoplastic molding for technical applications, or for direct spinning into fibers and filaments.